Gauges are well known in many different configurations for providing an indication of the fluid level in a vessel. Most gauges include a float mechanism which moves in response to changes in the liquid level in a tank. Typically the float mechanism is connected in a movable fashion to a resistive element. As the point of contact along the resistive element changes as the float moves in response to changes in liquid level, a signal can be generated indicating the liquid level.
Heretofore, one limiting factor on the life of gauges is corrosion when the gauges are in contact with liquids such as tap water, sea water, acids, bases, and liquid fertilizers, which support electric-chemical or chemical corrosion. Because most fluid, including gasoline, liquified propane and liquified methane, contain electrolytes such as water vapors and small amounts of water, galvanic and electrolytic reactions leading to corrosion of metals occurs. The corrosion potential limits application of gauges where metal resistive elements are immersed in the fluid, or in contact with vapors over the fluid. Furthermore, such units generally have the drawback that the resistive wire is a thin winding which presents a rough surface creating uneven friction loads and the possibility of lost contact with the float mechanism. Furthermore, such resistive wires are usually made of iron nickel alloy which is highly susceptible to electrochemical corrosion. This is especially problematic because such wires are typically of very thin gauge. Furthermore, small pieces of contamination on the wire can create discontinuity in the reading. Obviously, corrosion problems increase as the corrosive properties of fluid increase.
There has been a need to provide a gauge that overcomes the disadvantages or prior assemblies. Also, there has been a need for a gauge for use in highly corrosive materials such as liquid fertilizers and strong acids and bases. The gauge of the present invention eliminates the float mechanism and the variable contact point. Thus, the gauge is much simpler to construct, and has the advantage that there are no moving elements which can become stuck or impeded. The gauge of the present invention also has the advantage of a relatively long resistive area which allows greater resolution and precision. The gauge of the present invention also has advantages of extended life by eliminating moving parts, reduce costs by simpler design and greater flexibility in a number of applications. Another advantage of the present invention is that the length of the gauge elements and the cross sectional area of the elements can easily be equipped to accommodate different sizes of tanks without requiring change in electric components to provide readout of the fluid level. The gauge has the advantage of being easily constructed.